It is generally known that shafts, the same as transmission shafts, are rotatably supported in a housing with one fixed bearing and at least one loose bearing with the bearings mostly arranged on the ends. Both radial forces and axial forces are absorbed and the shaft is axially fixed by the fixed bearing. The loose bearing, on the other hand, absorbs only radial forces and by an axially displaceable design of the bearing proper or of the fixing of the bearing makes it possible to compensate for a change in the length of the shaft concerned which can be caused by loading forces and by heat expansion.
It is also generally known in the bearing arrangement of a long shaft to provide located on the ends, such that excessive bending of the shaft is prevented. But especially in vehicle transmissions is basically designed to equip the bearing arrangement of the transmission shafts with as few as possible bearings and to construct it altogether as simple as possible. Hereby is obtained, on one hand, an easy assembly of the transmission and, on the other, the building space and the weight of the transmission are kept small. But the possibilities of construction for this are essentially determined by the type of construction of the transmission, particularly the number and arrangement of the transmission shafts.
DE 35 46 454 C2 discloses a twin-clutch transmission having a central first input shaft, a shorter second input shaft, designed as a hollow shaft, and situated co-axially with the first input shaft, and a layshaft situated parallel to both input shafts. The layshaft forms the output shaft and, for the purpose, has a bevel pinion on its engine-side end a bevel pinion for driving a bevel gear of an axle differential. The first input shaft is supported in the transmission housing by an outer and an inner tapered rolling bearing in an adjusted bearing arrangement in which each of the two bearings absorbs outwardly directed axial forces. In the same manner, the second input shaft is supported in the transmission housing by an outer and an inner tapered rolling bearing in an adjusted bearing arrangement.
The layshaft is supported in the transmission housing on its engine-side end by a fixed bearing formed of two tapered roller bearings and loose bearings situated centrally and on opposite ends, wherein the central loose bearing and the inner tapered bearing of the second input shaft lie in a common bearing plane and in a separate bearing plate of the transmission housing.
In DE 41 23 493 C2 describes a twin-clutch transmission having a central first input shaft, a shorter second input shaft, designed as a hollow shaft which is co-axially supported on the first input shaft, and a layshaft located parallel to both input shafts and in which the output shaft is formed by one other transmission shaft situated co-axially to both input shafts. The central first input shaft has a transmission-internal hollow shaft section with which it is supported on the output shaft by an inner fixed bearing and an outer loose bearing. The output shaft is supported by a fixed bearing in an output-side wall of the transmission housing.
The second input shaft is designed to be relatively short and supported by a fixed bearing in an input sidewall of the transmission housing. The first input shaft is supported on the input side by an outer and an inner loose bearing in the second input shaft, wherein the inner loose bearing is supported in about the same bearing plane as the fixed bearing of the second input shaft. The ends of the layshaft are supported in the transmission housing on the input side by a fixed bearing and on the output side by a loose bearing.
One other twin-clutch transmission having a central first input shaft and a shorter second input shaft, designed as a hollow shaft and co-axially supported on the first input shaft, is known from DE 101 53 014 A1. This twin-clutch transmission has two layshafts, situated parallel to both input shafts, and together with both input shafts are arranged in a V-shape and are each connected by an output fixed wheel with a common output element. The second input shaft is axially floatingly supported on the first input shaft by two axial bearings situated on the ends. The first input shaft is supported in a wall of the transmission housing via a fixed bearing situated on its engine-remote end and by two loose bearings in the second input shaft. The second input shaft is radially supported by a loose bearing in an engine sidewall of the transmission housing in the bearing plane of which is also situated the outer loose bearing of the first input shaft.
Contrary to the aforementioned transmission, in the Applicant's unpublished DE 10 2005 005 163.4, a twin-clutch transmission is introduced which, together with a central first input shaft which is connected on the engine side with a first clutch of a twin clutch, a shorter input shaft, designed as a hollow shaft, and co-axially situated on the first input shaft, the same as connected with a second clutch of the twin clutch, and a main shaft disposed parallel to both input shafts, in addition, has one pinion shaft disposed parallel to the main shaft and connected with the main shaft by an drive constant formed by two fixed wheels and disposed in the area of the transmission-internal end of the second input shaft between two pairs of toothed gear wheels.
This invention is based on the problem of providing an optimal support of the transmission shafts for the twin-clutch transmission disclosed in DE 10 2005 005 163.4 and for similarly constructed twin-clutch transmissions.